In the past number of years there has been a continuously increasing surge of interest in winter sports activities, particularly those activities which need a snow base for operation, e.g., skiing, snowmobiling, snow-shoeing and the like. Unfortunately, in many areas of the world the natural snow fall is not predictable nor sufficient to assure continuous operation during the season of sports areas and resorts having facilities for such winter sports.
In more recent years continuity of operation and a good snow base has been gained by the use of artificial snow-making machines and apparatus. With such equipment snow-based winter sports activities have been continuously operated during the winter season and extended to geographical areas of the United States; for example, as far south as North Carolina, Virginia and Tennessee even though there is usually not sufficient natural snow in these areas to permit such sports on a regular basis during the season.
With artificial snow making equipment it is essential only that there be an ambient temperature below about 32.degree. F. (0.degree. C.) for a period sufficient to permit snow making to continue until an adequate depth of snow is deposited on the area, terrain or slope desired to be covered. In areas of North Carolina and Tennessee, for example, during a typical winter sports season there may be only 25 days with good conditions for making artificial snow. Farther north in Ohio 30 to 40 days snow making operation ordinarily can be expected and in Michigan 50 days or more are not uncommon. Therefore, it is important for effective operation that large volumes of snow be made rapidly during those periods when conditions are right for mechanical snow making.
The snow making apparatus and machines which have gained widespread commercial acceptance to date have all suffered from certain drawbacks which have led either to a low quality of snow, e.g., the deposited snow is too wet and/or resulted from a high energy input to low quantity of snow particle generation, thus being of a relatively low efficiency.
Illustrative of such apparatus is that disclosed by Pierce in U.S. Pat. No. 2,676,471. This machine mixes compressed air with water within a spray nozzle to effect particle formation of the water along with a cooling of the water which results from the adiabatic expansion of the compressed air. In commercial practice it has been found that the Pierce machine is highly susceptible to nozzle freezing. Additionally, excluding wind factors, this apparatus depends on the force of the compressed air and water themselves to move the freezing water particles beyond the immediate area of the nozzle. The heat of fusion of the freezing water particles requires considerable energy and results in excessive localized heating of the immediate ambient air when inadequate compressed air is present. Therefore, the volume of compressed air, and accordingly compressor capacity, required per unit volume of deposited snow is relatively quite high. While the examples in U.S. Pat. No. 2,676,471 show less than 1 gallon per minute, it is my understanding that this apparatus as modified since the patent issued and in operation under optimum atmospheric conditions, at a maximum, typically can crystallize about 20 gallons of water per minute, per nozzle, per 200 cubic feet per minute of compressed air. While Pierce, in column 7, alludes to oscillation of nozzles, he does not show oscillation in a manner such that the newly deposited snow is not touched by additional snow produced immediately thereafter. In fact, Pierce nowhere teaches that the battery of nozzles employed in his apparatus actually could oscillate, only that they may be oscillated during operation. Further, even if these were to be made to oscillate together, or independently, there is no way that snow particles resulting from such operation could be deposited on an area different from that struck by the immediately preceding particles. To oscillate the nozzles of the Pierce apparatus at best would provide a fan pattern or overlapping fan shape patterns where the particles generated by the nozzles would always be overlapping with the zone of the immediately preceding particles and contacting the portion of snow which was laid down immediately before. There would be no covering of a location different from that covered by the immediately preceding generated particles.
More recently, as described in my U.S. Pat. No. 2,968,164, a different type snow making apparatus has become commercially available. This machine includes a high powered fan for providing a substantially unidirectional high volume of air at substantially atmospheric pressure and in combination therewith an independent water spray providing means downstream from the fan. This water spray means is designed and positioned to provide a water spray which is injected into the high volume air movement from the fan at a rate and in a quantity sufficient to achieve crystallization of a substantial amount of the spray droplets and deposition of these as snow. This machine has the advantage that it operates without requiring the use of compressed air although compressed air can and often is used for nucleation. Other nucleation methods may also be used.
Eustis in U.S. Pat. No. 3,703,991 utilizes the principles of my earlier U.S. Pat. No. 2,968,164; i.e., a large fan is employed to move particles away from a spray nozzle, but also provides additionally a system wherein compressed air and water are mixed within a first seeding nozzle as taught earlier by Pierce and water is added to the fan moved air by a second exterior nozzle. The seeding nozzles are disposed within the protective cowling of the fan; this can lead to frozen nozzles and increased mechanical difficulties in cleaning and repair. In commercial operations this apparatus has been shown to convert as much as two hundred to 250 gallons of water per minute into snow under optimum conditions.
Ericson, et al. in U.S. Pat. No. 3,610,527 have taught another modification of my eariler U.S. Pat. No. 2,968,164 whereby with an 18 or 20 inch fan blade from about 3 to about 140 gallons of water per minute can be converted into snow depending on the rate of rotation of the fan propeller, ambient temperature and relative humidity, and the temperature of the feed water.
Rice, in U.S. Pat. No. 3,838,815, described a blower projecting air and spraying water particles into the air stream. Hanson U.S. Pat. No. 2,968,164 was not cited in this patent. No significant commercial use of the Rice system is known to me.
A still more recent apparatus for making and depositing snow which has been observed in use comprises in combination a means for providing a substantially unidirectional large volume movement of air at atmospheric pressure and at a temperature below about 32.degree. F., a first nozzle means providing a high velocity water spray directed into the unidirectional air movement at a first angle with respect to the direction of air movement and a second nozzle, distinct from the first nozzle, providing a high velocity air stream or air-water stream directed into the unidirectional air movement at a second angle with respect to the direction of movement of the air. The first and second nozzles are oriented with respect to one another such that during operation the air stream intersects the water spray at a point remote from the first and second nozzles. Operation of this apparatus provides a high dispersion of the water particles throughout the unidirectional air movement with resultant crystallization into snow particles and their deposition.
As indicated hereinbefore, each of these apparatus generates snow, some at higher volumes and rates than others, but all deposit the resultant snow particles on a fixed area, or in the case of oscillation of the Pierce battery of nozzles, over a wider area, but in any event such that substantially all of the generated snow particles fall onto particles that were immediately previously generated. (It is recognized, of course, that because of vagaries of natural air currents and wind some of the resultant snow may blow or drift away from the intended deposition site.) Generally, however, the bulk of the snow is aimed at and strikes a given area and as a predetermined depth is built up over a period of from less than 1/2 hour to 24 hours or more the apparatus is then moved and repositioned to have the snow deposited on a different area. Not only is this operation cumbersome and requires manpower to shut down and bodily move the rig from position to position, but more importantly, the continuous deposition of this still wet snow particles onto previously deposited particles which have not yet completely frozen can lead to icing conditions which are not desired by ski area operators and skiers alike. Alternatively, if the quantity of water put through the machine is reduced, the quantity of snow produced is reduced with the attendant economic disadvantages.
Now, unexpectedly, I have discovered a new and useful improvement in snow making apparatus of the type which operate by introducing water particles, e.g. a water spray, into a large volume unidirectional mechanical movement of air ordinarily generated by a fan or propellor at substantially atmospheric pressure and at a temperature of below 32.degree. F. whereby volumes of water much larger than useable heretofore are converted into high quality snow particles and these effectively directed over a greater area than realized heretofore. Further, the resultant snow product is deposited onto previously deposited snow which has aged or has completely frozen into relatively dry crystalline snow particles, thus producing a particulated snow base of excellent quality.
The present invention will be fully understood from the detailed description presented hereinafter in the specification when read in conjunction with the Figures of the drawing.